Typical marine vessels generally have a first engine dedicated to propulsion of the vessel as well as a second engine to provide electrical power throughout the vessel. The second engine is also used to power other auxiliary devices such as pumps and electric generators. This is problematic such that two engines are required to provide separate functions, often having one engine run at a high percentage of its operation capacity to run one function while the other is being idled or used at a low percentage of its overall capacity performing another function. Furthermore, this type of operation can lead to premature wear or required service of one or both of the engines as the engines are not able to share the responsibility of the total load and operate more consistently and at less burdensome percentages of their overall capacities.
Additionally, marine vessels, when not traveling or operating on the open waters are docked and connected to shore power. In this situation, the vessels are typically dependent on the electricity from shore power connection and are not able to efficiently run the engines to reduce the amount of electricity required from the shore. This type of operation generally increases the vessel's operating costs.
In other marine vessel situations, two engines are setup in tandem to run a single propeller. Unfortunately, this type of operation, without the proper droop set up, does not allow for the engines to run equally and does not allow for the engines to be set up to run at predetermined percentages of each of the engine's total torque requirements. Rather, the engines would fluctuate.
It is often necessary in the marine industry to operate a propulsion engine in either a tandem application or a power generation application. Without droop, current electronic governors on propulsion engines operate in an isochronous mode and does not allow for stable operation in either power or tandem generation modes. An engine running isochronously is an engine always running at the same speed based on a given load. The idea of droop is not new to internal combustion engines. Droop allows the engine to run at different speeds for a given load. Current methods of droop generally calculate droop at a fixed speed. These methods do not account for multiple operating modes that a marine propulsion engine can operate in, such as smoke limiting, engine derate, or other programmable torque modes. By not accounting for the various operating modes, engine operation is not generally being performed to minimize fuel consumption and maximize engine life.